In light of recent reports of clotting events following Astra Zeneca (AZ) vaccine in Europe - we have been frequently asked questions regarding the safety of AZ vaccine in patients with previous clot events and/or blood problems.

We would like to draw your attention to the following publication from Australian Technical Advisory Group on Immunisation (ATAGI) on the 25th March 2021.

The salient points of this publication:

• There is no increase in the rates of general thromboembolic disorders after vaccination over expected rates, noting these conditions occur commonly in the absence of vaccination.

• It is not known whether the clot event is linked to vaccination. Cases of specific clot called “Cerebral Venous Sinus Thrombosis or CVST” reported overseas have mostly occurred 4 to 14 days following the AstraZeneca vaccine and have been rare (varying reports of 1 to 8 per million doses of vaccine given). Further studies in these patients are ongoing to understand if there is a potential link with vaccination.

• Overall, ATAGI emphasises that the benefits of the COVID-19 vaccine far outweigh this potential risk.

• The recommendation considers that there is no evidence of a risk of clot after COVID-19 vaccination in people with a history of clotting conditions. This includes those with clotting events in legs or lungs; people with risk factors for thrombosis (such as use of oral contraceptives or smoking); people with thrombocytopenia (low platelets that can occur with clotting conditions); people with known clotting disorders; people on blood-thinners (e.g. warfarin) and people with a history of cardiovascular disease (such as heart attack or stroke).

The publication also recommends that COVID vaccines should be deferred for patients with 2 very rare, specific blood clot conditions called “Cerebral venous sinus thrombosis or CVST” and “Heparin induced thrombocytopenia or HIT”. This is until further information from ongoing investigations in Europe is available and is only a precautionary measure.

We need to emphasize that these are very rare conditions; most patients with clotting disorders do not have these conditions. You can speak to your GPs or our haematologists if you have any concerns, prior to receiving the COVID vaccine.

For full publication, visit this link: www.health.gov.au/news



Disclaimer: This information is up-to-date at the time of sending, on 26^th March 2021. Please check for further updates regarding this topic to ensure that the information is still current.

Dr Pohan Lukito

Consultant Haematologist

MBBS, B Med Sci, FRACP, FRCPA